This invention relates to a method and apparatus for installing elongate objects such as pin or post terminals on substrates such as printed circuit boards. More particularly, this invention relates to a method and apparatus wherein pins discrete from and removably carried by a flexible plastic carrier strip are directly inserted into a circuit board.
A polyester carrier strip of this type is disclosed in a commonly assigned copending U.S. patent application Ser. No. 288,851, filed Sept. 13, 1972, for "Pin Terminal Carrier Strip". The strip is comprised of an elongate member having a generally U-shaped transverse cross election. The opposite legs of the U-shaped member are provided with aligned carrier slots for holding pins in a generally orthogonal relationship to the strip. Relief slots are also provided in these legs to facilitate transport of the strip by sprocket wheels or the like, while the pins remain seated in the carrier slots. For such transport purposes, the base of the U-shaped member includes indexing apertures cooperable with the sprocket wheels.
In the above-mentioned application, the disclosure of which is hereby incorporated by reference, the carrier strip previously described is discussed in the context of overcoming drawbacks associated with prior pin installation techniques.
One such prior technique is that of manual, individualized installation. This type installation not only is time consuming by reason of the large numbers of pins usually involved and their handling difficulty attributable to size, but also may not be entirely satisfactory from the standpoint of obtaining reliable pin orientation perpendicular to a board without pin damage.
Although some of the problems associated with manual installation may be overcome through prior proposals for automated handling of loose pins with a vibrating hopper or similar arrangement for orienting the pins, it will be appreciated that significant room for improvement exists. Particularly, several drawbacks may be encountered with such arrangements in the areas of the speed of operation, complexities in relation to pin handling once the pins are oriented, etc.
As pointed out in the previously identified application, there have also been prior proposals directed toward providing carrier strips for pin terminals and other types of contacts. However, such proposals may not be entirely acceptable for a variety of reasons.
For example, in some cases heat is required for contact removal. Often the flexibility of the carrier strip is not particularly suited for adequate handling in an automated manner. Disposal costs in connection with some strips made from certain materials may be prohibitive. In addition, complex equipment is often contemplated for removal of the contacts from strips with which the contacts may be integral.
The flexible, easily handled carrier strip of the aforementioned application is intended to aid in overcoming problems of the sort previously noted. In accordance with the teachings of that application, removal of the pins from that strip may be accomplished oy applying a force to the pin either in a direction transverse to the extent of the strip or in an axial direction. With transverse removal, equipment in addition to that used for removal is required for insertion of the pins. With axial removal, a post employed for pin removal may also be used for direct pin insertion. During direct insertion of the pin, the yieldable legs of the U-shaped strip are displaced by the recessed post which embraces the pin and axially translates it into a position of press fit reception in a circuit board hole.
The present invention relates to direct pin insertion of this type. Specifically, the present invention is concerned with retaining the advantages of single stroke pin removal and installation as disclosed in the above noted application, while minimizing or obviating problems associated with such a direct insertion technique.
In this connection, it will be recognized that among the difficulties that might be encountered with automated pin insertion techniques is that of insuring reliably reproducible location of the pins at a pin insertion zone aligned with the circuit board hole to receive the pin. Although the flexibility of a pin carrier strip enhances its handling and transport characteristics, that same flexibility might contribute to misalignment of the pins at the insertion zone, both as an initial matter and during pin insertion. Similarly, where direct insertion is attempted, misalignment problems might result from inadequate provision for carrier strip advancement.
Problems such as these can be somewhat remedied by using equipment separate from the carrier to grip and orient the pins at the insertion zone. However, provision of such equipment could give rise to potentially higher equipment costs and lower operational speeds. Conversely, elimination of such equipment could create other difficulties associated with force and positional relationships between the pin and the members acting on the pin during insertion.
One previous machine of the present assignee, not of the direct insertion type, utilized removal equipment to transversely remove the pins from a carrier strip. This equipment also aided in insuring correct positioning of the pins for insertion. It would, however, be desirable to eliminate the need for such equipment by reason of the earlier noted potentially higher cost and lower operational speed factors, etc. associated therewith.
Moreover, other elements of that machine would not be necessarily compatible with direct insertion techniques. For example, carrier strip guidance by utilizing jaws to grip the base of the generally U-shaped strip could present interference with movement of an insertion ram if direct insertion were attempted. Moreover, these jaws could undesirably rigidify the strip to render it unsuited for both continuous feed and direct insertion without breaking the strip.
In addition, force cooperation between an insertion ram and the pins to be inserted involved, in that machine, the use of sliding blocks that needed to be displaced during continued downward ram movement to effect insertion. The mass of the blocks and control of the block movement through cooperation with an anvil gives rise to the need for controlling several mechanical movements and the possibility of jamming.
Other prior proposals which do relate to direct insertion of pins from a carrier strip are disclosed in Bakermans U.S. Pat. No. 3,605,237, issued Sept. 20, 1971, and in De Shong U.S. Pat. No. 3,307,244, issued Mar. 7, 1967. According to proposals such as these, the carrier may be advanced by incrementally pushing on a metal strip with which the pins are integral. Guidance of the strip along a structurally defined path may be provided. At the insertion location, the pins are gripped by alignment clamps, and a ram and anvil like combination is employed to sever the pin from the strip and insert the pin.
It will be recognized that, although such machines might be desirable for some purposes, the may not be entirely acceptable for a number of reasons. Some of these relate to the particular type carrier strip to which these proposals are essentially restricted, while others are more general in nature.
For example, the need for equipment and sequencing associated with severance of the pins from the strip may present difficulties. Similarly, use of the particular type feeding and guidance techniques for the relatively rigid strip might not be acceptable in the case of a flexible strip such as that with which the present invention is most particularly useful. Pin orientation equipment distinct from the carrier might, as earlier noted, also be undesirable.
Numerous other difficulties associated with carrier strip feeding and handling, pin orientation, and pin insertion can be envisioned.